Precision Barometer/Altimeter

with temperature readout

Based on the MS5534 pressure sensor made by the Swiss company INTERSEMA (specialized in pressure measurements), with one metre resolution in altitude, this circuit will also give you absolute pressure, temperature, and even the time of day. The microcontroller used in the instrument is the now well established PIC16F876.

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CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
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New software that solves the problems with the real-time clock is now available from our website (ref. 040313-11.zip).

Problems with the real-time clock may be solved by downloading updated software from our website. A 56-pF capacitor between pin 12 of IC1 and ground will improve the clock accuracy.

Due to a change in the control software, a few small modifications are required on PCB no. 040313-1. The modified PCB design can be downloaded here (ref. 040313-PCB.pdf). PCBs already supplied through Readers Services, or made at home using the artwork originally supplied, may be modified as detailed below.The two PCB tracks leading to pin 1 (MCLR) of IC2 are cut as close as possible to the IC pin and then connected to each another only, using a small piece of wire. The track between pin 4 (RA2) of IC2 and junction R7/S1 is cut in the vicinity of pin 4. Next, the interrupted track coming from R7/S1 is connected to pin 1 of IC2.